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Looks like to me you have a EShopps WD-125CS sump that has been customized by a past owner.

You can customize a sump to add on just about anything you can think of that is useful in a aquarium. They could have used those hole for many different things such as temp and pH sensors (the smaller holes) for a CO2 controller and a temp sensor for a heater controller (assuming they used a higher than typical water level). I would guess the large hole was used for a return line back into the main tank so they could use a cover on the sump and reduce evaporation. Just a couple of guesses on my part base on how I have commonly seen sumps like this set-up and used by fellow hobbyist where I live. You could easily seal those and use the sump in a more traditional set-up if that is what you prefer.

In reef tank set-ups I have seen hole like that drilled for a wide range of sensors and auto-top up systems. Although, you typically don't see wet-drys used on any type of marine aquarium.

If you take your time to do the research FIRST, you can successfully set-up and keep ANY type of aquarium with ease."Not using a quarantine tank is like playing Russian roulette. Nobody wins the game, some people just get to play longer than others." - Anthony CalfoFishless CycleCycling with FishMarine Aquarium Info [URL="http://saltwater.aquaticcommunity.com/"]

If you are not too concerned about the looks, a small pc of acrylic glued over top of them using the proper glue/solvent meant for acrylic.

Last edited by Cliff; 06-30-2014 at 12:11 AM.

If you take your time to do the research FIRST, you can successfully set-up and keep ANY type of aquarium with ease."Not using a quarantine tank is like playing Russian roulette. Nobody wins the game, some people just get to play longer than others." - Anthony CalfoFishless CycleCycling with FishMarine Aquarium Info [URL="http://saltwater.aquaticcommunity.com/"]